Electromagnetic switching devices are known. By way of example, reference is made to EP-A-0 505 194.
Electromagnetic switching devices such as power circuit breakers and contactors contain magnetic drives which include a solenoid, a yoke and an armature. The yoke and the armature in this case consist of magnetizable material, for example iron sheets. If an inrush current is applied to the solenoid, a magnetic flux is produced in the yoke, exerts a force on the armature and picks it up. The armature is consequently displaced into a pickup position.
In the case of a contactor, the displacement of the armature has the effect that switching contacts connected to the armature are moved, and consequently main electrical contacts of the switching device are closed. Once application of the inrush current to the drive solenoid is completed, the armature is moved back into a starting position by restoring springs and, as a result, the contacts are opened.
In the case of power circuit breakers, magnetic trips in which a current to be monitored flows through the drive solenoid are used. If this current exceeds a predetermined value (that is to say the inrush current), the armature is displaced and, as a result, the breaker latching mechanism is actuated, which in turn brings about the opening of the contact.
In the prior art, the yoke and the armature include laminated cores which are produced from individual iron sheets that are connected to one another—for example by rivets. The production from individual metal sheets that are insulated from one another is necessary in this case in particular for the avoidance of eddy currents and associated eddy current losses.
In the prior art, it is disadvantageous in particular that, as a result of the sheeting, only limited degrees of freedom of form are possible and that the sheets can only be connected to the housing and actuating elements by appropriate fastening elements. The solenoid also has to be connected to the housing or the yoke by a separate insulating frame. Furthermore, in the prior art, the striking together of the yoke and armature has the effect of restricting the service life of the magnetic system.
It would be desirable for the yoke and the armature to be able to have any desired three-dimensional structures, which would make it possible for the magnetic circuits to be optimally configured. It should also be possible for the yoke, the drive solenoid and the housing to be connected to one another in a simple and low-cost way, in particular without additional fastening elements. Furthermore, there should be good thermal coupling, to allow any heat loss occurring to be dissipated and so-called hot spots to be avoided. Furthermore, the service life of the magnetic system should be just as long as the mechanical service life of the switching device.